1. Field of the Invention
This invention relates to an improvement of a rotary drum type paper stock cleaning apparatus provided by Japanese Patent No. 2709300.
2. Related Art
A paper stock cleaning apparatus disclosed in Japanese Patent No. 2709300 comprises a rotatably horizontally disposed air-permeable and water-permeable drum, one end of which is provided with a paper stock inlet port and the other end of which is provided with a paper stock outlet port, a cleaning water supply device for supplying cleaning water to a paper stock within the air-permeable and water-permeable drum, a plurality of baffle plates extending in a peripheral direction along an internal peripheral surface of the air-permeable and water-permeable drum and spacedly arranged in an axial direction, and a plurality of paper stock cleaning zones divided in the axial direction by the baffle plates and being formed between the baffle plates.
A plurality of raking plates are spacedly arranged in the peripheral direction between adjacent baffle plates and adapted to rake the paper stock liquid in the paper stock cleaning zones in a direction of rotation of the drum, and a paper stock flow-through space for allowing the paper stock to flow therethrough in the peripheral direction is formed between an external edge of the inclination raking plates and an internal peripheral surface of the air-permeable and water-permeable drum. The paper stock loaded through the paper stock inlet port is allowed to move, zone by zone, through the paper stock cleaning zones formed between the baffle plates and brought to the paper stock outlet port, and the paper stock, when in the paper stock cleaning zones between the baffle plates, is raked up in the peripheral direction by the raking plates in accordance with rotation of the air-permeable and water-permeable drum, falls by force of gravity, and back flows through the paper stock flow-through space, repeatedly.
The paper stock loaded through one end of the air-permeable and water-permeable drum, as in the above related art, is raked up in the peripheral direction by the raking plates and falls repeatedly in the paper stock cleaning zones, and finally brought to the paper stock outlet port from the paper stock inlet port by moving, zone by zone, through the paper stock cleaning zones. During the above-mentioned procedure, satisfactory agitation and dispersion of the paper stock are enhanced and filtrate is discharged through a peripheral wall of the drum for the paper stock zones of each stage divided by the baffle plates, and effective substitution cleaning is carried out. A cleanly washed paper stock is obtained in the paper stock cleaning zone of the final stage and discharged.
The important feature of the above paper stock cleaning apparatus resides in that the paper stock cleaning zones are formed and the raking plates are provided to the respective cleaning zones so that the paper stock in the cleaning zones is raked up by the raking plates and falls, repeatedly, thereby enhancing filtration and dehydration in each cleaning zone, so that the cleaning effect is remarkably improved.
It is, therefore, an object of the present invention to provide a paper stock cleaning apparatus in which the paper stock cleaning zones and the raking plates provided to the respective cleaning zones are synergistically increased in function and the effect of cleaning of the paper stock is enhanced significantly.
To achieve the above object, a paper stock cleaning apparatus according to the present invention comprises, as in the above-mentioned related art, a rotatably horizontally disposed air-permeable and water-permeable drum, one end of which is provided with a paper stock inlet port and the other end of which is provided with a paper stock outlet port, a cleaning water supply device for supplying a cleaning water to the paper stock in the air-permeable and water-permeable drum, the paper stock being agitated while having cleaning water applied thereto during the time the paper stock travels from the paper stock inlet port to the paper stock outlet port, a filtrate (substitution cleaning water) being discharged downward of the drum.
The paper stock cleaning apparatus further comprises, as in the above-mentioned related art, a plurality of baffle plates that extend in a peripheral direction along an internal surface of the air-permeable and water-permeable drum and that are spacedly arranged in an axial direction, paper stock cleaning zones divided by the baffle plates in the axial direction are formed between every adjacent pair of baffle plates, and raking plates for raking up paper stock liquid in the cleaning zones in the peripheral direction are spacedly arranged in the peripheral direction between the adjacent baffle plates.
All or a part of the raking plates in the paper stock cleaning zones are disposed in inclined postures with respect to the axis and all or a part of the raking plates are allowed to project inwardly beyond internal edges of the baffle plates, so that even a part of the paper stock that overflows to the next zone by overriding the baffle plates are raked up and then fall, thereby enhancing the cleaning effect.
Preferably, the projecting portions of the raking plates are inclined so as to form a relief angle with respect to the direction of rotation of the air-permeable and water-permeable drum. Owing to this arrangement, the falling of the paper stock as a result of raking up of the paper stock is performed smoothly.
Moreover, the inclined raking plates are oriented with a downward gradient towards the paper stock outlet port so that a part of the paper stock raked up by the inclined raking plates flows to the paper stock cleaning zone adjacent to the paper stock outlet port through the angle at which the raking plates are inclined. Owing to this arrangement, the flowing of the paper stock is enhanced between the paper stock cleaning zones.
A paper stock flow-through space for allowing the paper stock to flow therethrough in the peripheral direction is formed between an external edge of the raking plates and an internal peripheral surface of the air-permeable and water-permeable drum, and the external edge of each of the raking plates is formed in a curved plane generally in harmony (complementary) with that of the internal peripheral surface of the air-permeable and water-permeable drum, such that a space between the external edges of the inclination raking plates and the curved plane of the internal peripheral surface of the air-permeable and water-permeable drum is generally uniform over an entire length of each raking plate. Owing to this arrangement, the back-flow of the paper stock is uniformly performed.
Of course, as in the above-mentioned related art, the paper stock flow-through space may be formed between the external edges of the raking plates other than the inclined raking plates and the internal peripheral surface of the air-permeable and water-permeable drum.
Accordingly, the paper stock, in the cleaning zones between the baffle plates, is raked up in the peripheral direction by the baffle plates and falls by force of gravity, repeatedly. In this manner, dispersion and cleaning of the paper stock are remarkably enhanced.